The present invention relates to a manufacturing method of a resin container to which a decorative design having a higher sense of togetherness can be applied by changing a thickness of a coating layer partially formed in a container body at a boundary portion between the coating layer and a part where the coating layer is not formed.
In recent years, a demand for resin containers has been increased. For example, various commercial products such as food products like beverage products or sanitary goods like a body soap or a shampoo are accommodated in resin containers and sold over counters. Under such circumstances, there are commercial products which have a tendency that conformations of their containers are similar because of characteristics of the commercial products, and it is often the case that similar commercial goods are accommodated in similar containers and sold.
On the other hand, general consumers consider a quality, a price and others of each commercial product when deciding purchase. Although it is a matter of course, an impression given by an appearance of a commercial good may have a great influence of a judgment upon purchase in some cases. In particular, when comparing commercial products which have almost no difference in quality, price and others, such a tendency becomes strong. Further, a container which is an appearance itself of a commercial product largely concerns formation of a commercial product image. In general, it can be said that earnings of a commercial product tend to increase when an excellent commercial product image is formed, but earnings of the commercial product tend to fail to rise when a bad commercial product image is formed. In this manner, an appearance of a commercial product, i.e., an impression which is given to consumers by a design of a container is very important in order to drive the consumers to buy.
Meanwhile, as a resin container in which the above-described commercial product is accommodated, one manufactured by a molding method called “blow molding” is generally used (see, e.g., a paragraph [0010] of Patent Reference 1: Japanese Patent Application Laid-open No. 2000-142662, a paragraph [0012] of Patent Reference 2: Japanese Patent Application Laid-open No. 2000-238116 or the like). In blow molding, a molten material (a parison) extruded in a cylindrical shape from an extruder is held by a metal mold and air is blown into this material, thereby obtaining a hollow molded piece. Each of Patent Reference 1 and Patent Reference 2 discloses a multi-layer thin container which is provided with desired functional characteristics by adjusting an extruding quantity of a resin forming one layer when extruding a parison having a double-layered structure.
In such a resin container, a geometric design is applied and, on the other hand, a label sticker on which a commercial product name or the like is printed is put, or a film material such as a shrink label or a stretch label is attached so that commercial goods are discriminated. Further, there is appropriately performed direct printing on a container surface by appropriate printing means such as screen printing, uniform coloring of an entire container by adding a pigment or the like to a material resin forming the container, and others. These methods are generally utilized in order to apply a design using colors or colored patterns to containers.
In the method putting a sticker or attaching a film material, however, a sense of togetherness with a container is hard to be obtained, and the design is greatly limited. Furthermore, in such containers, labels must be separated at the time of discard, and hence it can be considered that containers with stickers or film materials are distantly respected by consumers. Moreover, in the method of performing direct printing on a container surface, for example, printing is difficult unless a relatively flat surface is provided, and hence there is a restriction in printing. Additionally, these methods are disadvantageous in terms of a manufacturing cost because they require a secondary process. On the other hand, in the method of coloring a container by adding a pigment or the like to a material resin, since molding and coloring can be simultaneously performed, this method is less disadvantageous in terms of a cost. However, a state of coloring is uniform in an entire container, and there is a drawback in which a change in colors cannot be expected.
As described above, in the conventional methods, various problems have been pointed out when applying a design using colors or colored patterns to containers. Although a container which appeals to consumers is demanded, an effective alternative idea has not been proposed yet. Even in Patent Reference 1 and Patent Reference 2 mentioned above, such design problems have not been taken into consideration at all.
The present invention is proposed in order to solve the above-described problems of a prior art, and it is an object of the present invention to provide a manufacturing method of a resin container which further appeals to consumer and enhances its value by, e.g., applying a decorative design having a high sense of togetherness to the container itself with a high degree of freedom.
Further objects and advantages of the invention will be apparent from the following description of the invention.